Safety Analysis of Urban Arterials under Mixed-Traffic Patterns in Beijing

Many studies have dealt with modeling crash occurrences on urban arterials. There is a dearth of research on urban arterials with mixed-traffic patterns in China, however, because of the large traffic flow volume of bicyclists and pedestrians in most Chinese cities. This study investigates the risk factors associated with severe crash occurrences on arterial roads in Beijing. Through use of the generalized estimating equations modeling technique with a negative binomial link function, statistical relationships were established to relate severe crashes to a variety of factors related to geometric design, traffic control, and other traffic-related characteristics. Crash records from 2004 to 2007 for 108 signalized intersections and 123.5 km of road segments were used to estimate the models. Results showed that arterial roads with heavier traffic volumes, more road lanes, and higher speed limits tended to have more severe crashes. Medians were helpful in reducing severe crash risk. Higher risks of severe crashes were generally associated with intersections having small angles and countdown signals and road segments having higher side-access densities and the presence of bus stops. With regard to nonmotorist protection facilities, results revealed that a combined use of crosswalks and overpasses was the most desired pedestrian-crossing facility for safety, especially at sites with heavy traffic or sites located in primarily residential areas. Barriers that separated bikeways from roadways on minor roads were found effective in significantly reducing severe crash risk at intersections.